What would Paul's own people and the Roman world have done if he had told them what he saw in heaven?
Paul's own people and the Roman world would have fallen down and worshiped him if he had rehearsed what he had seen and heard in glory. God could not permit that, so He placed a stigma on him that he could not repeat what he had seen and heard.
Les explains that if God had permitted Paul to repeat what he had seen and heard, the human race would have worshiped him. Paul was just as human as anyone and never expected worship from his converts; he was not God. If Paul had rehearsed these things with his own people or even the Roman world in general, they would have fallen down and worshiped him. God could not permit that, so He placed a stigma on Paul that he could not repeat what he had seen and heard. Les notes this happened fourteen years back, early in Paul's missionary career in the early 50s. Les also suggests that during intense suffering, as Paul was leaned over the stake and whipped, what he saw and heard in glory constantly sustained him.